Some electronic devices, such as cellular phones and smart phones, have menus or graphical user interfaces that are rather complex. In order to navigate through these menus, a user may move his finger over a navigator, which causes an icon associated with the menus to move. As electronic devices get smaller, the navigators must also get smaller so as not to limit the size of the electronic devices.
A key parameter in accomplishing a low profile Optical Finger Navigation (OFN) system is controlling the total vertical distance from the object to the image. One of the approaches used in prior solutions, is to fold the optical system with the use of two prisms.
In this approach, the field of view and/or the size of the image formed is limited by the vertical space (or thickness) of the prism. From another perspective, the lowest OFN system height achievable with such an approach is limited by the required field of view and/or image size requirements. Thus, prior solutions are self-constrained in their minimum allowable vertical height.